HeLa cells. Coloured scanning electron micrograph (SEM) of a HeLa cells in culture. HeLa cells are a continuously cultured cell line of immortal human cancer cells derived from cervical cancer cells. As they are immortal they thrive in the laboratory and are widely used in biological and medical research. Since being discovered in the 1950s, experiments on HeLa cells have played a role in developing advances like the polio and COVID-19 vaccines, treatments for cancer, HIV, AIDS, and much more. About 55 million tons of these cells have been used in over 75, 000 scientific studies around the world. Cancer of the cervix (the neck of the uterus) is one of the most common cancers affecting women. Magnification: x500 when printed at 10 centimetres wide.